Most walls from spells must be straight lines. I'm wondering how free am I am with placing them - can I place a wall within squares or only at the borders? Can I place one diagonally over 2 squares, or must a wall follow the square borders on the minimap?

And for the Wall of Smoke spell from the Spell Compendium, p235:

"A straight wall whose area is up to one 10-ft. square/level"

Does this mean that the Wall fills the square? Can I place the wall on enemies, more specifically: on squares that are occupied by enemies?

2 Answers
2

About the placing over enemies: Wall spells that don't allow to place the spell in an occupied square will usually tell you so, like Wall of Stone. As a rule of thumb, spells that create a wall that characters can walk through usually allow you to do that (there are exceptions, like the Prismatic Wall). In this respect, since there is a precedent, not saying you can't means you can.

The Wall must, by exact wording, be a straight. Since its area can be as big as 10' per caster level, it can be any type of rectangle that stays within those bounds; "up to one 10-ft. square/level" means that that's your max size, it doesn't necessarily have to be the full size.

The placement depends on how religiously do you take the map grid... If you live and breath by it, then you must always have it occupy an area that covers all the grid squares it's on completely, so that there are no partially occupied tiles; this means no diagonals. If you allow some leeway, you can place it anyway you want, and characters in a tile partially covered by the wall would either have penalties to their actions but be unaffected or be affected but with a lowered save, at the DM's discretion.

I believe so. I believe what this means is that it's actually a straight line made of 10x10 blocks, so basically you get four squares in each (5-foot grid is normal, right?), then you can expand it in a certain direction.

So yes, it fills the square, you can put it on enemies and squares that they are in, so long as you are placing it as a straight line.

Do you have any references or rule text for that?
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MalaFeb 22 '12 at 19:40

"A straight wall whose area is up to one 10-ft. square/level" would imply by the terms area and square that it would cause its effects within squares, not just as a line. The 3.5 SRD would seem to be vague on this, but the terminology of the spell itself seems to me to be referring to an area, not just a line. To compare it to the Wall of Fire, which is definitely a line, "Opaque sheet of flame up to 20 ft. long/level or a ring of fire with a radius of up to 5 ft. per two levels; either form 20 ft. high".
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Kyle WilleyFeb 22 '12 at 20:12